Conversion of hydrocarbon oils



Jan- 2 1940- K. SWARQWQG@ .CONVERSN OF HYDRCRBCN CELS Filed Nov. 13,3,33%

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f mwN-JESFW INVENTOR KENNETH SWARTWOOD lllll ZDJOU AT TO RN EY PatentedJan. 2, 1940 CONVERSION F HYDROCARBON OILS Kenneth Swartwood, Chicago,Ill., assignor to Universal Oil Products Company, Chicago, Ill., acorporation of Delaware Application November 13, 1936, Serial No.110,627

Claims.

This appication is a continuation in part of my co-pending application,SerialNum'ber 28,803 filed June 28, 1935.

This invention refers to an improved process 5 for the treatment ofrelatively low-boiling distillates such as motor fuel or motor fuelfractions of poor anti-knock values, naphtha and the like underconversion conditions of elevated temperature and superatmosphericpressure regulated to effect a material improvement in the motor fuelcharacteristics of the distillate, particularly with respect toanti-knock value, without excessively altering their boiling range.

The invention is particularly advantageous as applied to the treatmentof low-boiling distillates, such as above mentioned, which are notadequately reformed in a single pass through the system. in that itprovides for the further treatment, under reforming conditions ofcracking temperature and atmospheric pressure, of selected intermediateconversion products of the reforming operation to which' the chargingstock is subjected. d

It is now well known that reforming operations of the character abovementioned ordinari'y produce only relatively small yields of liquidproducts of higher boiling characteristics than the charging stock, suchas intermediate liquid products corresponding to what is termed refluxcondensate in a conventional cracking operation. Furthermore,intermediate products of this general nature, produced in reformingoperation, are not ordinarily best adapted to further treatment underthe same 'cracking conditions as the lower boiling charging stock. Theymay, however, be cracked under independently controlled conditions toproduce additional yields of good quality gasoline, but the quantity ofsuch material produced in a reforming operation is ordinarily notsufcient to Warrant the use of a separate cracking zone. On the otherhand, such materias ordinarily comprise a product which is readilysaleable as good quality fuel oil. Therefore, in the present invention,I provide for removing this material from the system, or, when desired,I may utfl"z`e the same, in accordance with the provisions of theinvention,4 as a cooling medium for reducing the temperature. of thehigh heated productsfrom either or both cracking zones of the system, inorder to prevent vexcessive continued conversion of said heatedproducts.

In operations of the character above-outlined it is ordinarilynecessary, in order to produce a finished motor fuel of the desiredcharacteristics, to subject the light distillate product of the`reforming operation to stabilization toy free the same of undesirablelight ends and dissolved gases whereby to lower the vapor pressure ofthe final product to the desired degree and, in or- 5 der to insurerecovery of the maximum yield of motor fuel, it is particularlydesirable, in an operation of this character, to subject the gaseousproducts of the process to absorption for the recovery of theirdesirable components within the boiling range of the motor fuel product.

As a feature of the invention, the absorber oil utilized for recoveringsaid desirable high-boiling components of the gases' comprises theselected relativeyK low-boiling intermediate liquid prod- 16 ucts of theprocess, above referred to. This absorber oil includes high-boilinggasoline fractions produced by the reforming operation to which thecharging stock is subjected and which require further treatment toimprove their anti- 20 knock value. It may also include, when desired,higher boiling materials, such as naphtha, kerosene, kerosene distillateand the like, which in a conventional cracking or reforming operation,would be included in and comprise the low boiling fractions of the totalreflux condensate.

As another feature of the invention, -the enriched absorber oilresulting from the last described step of the process is preferablycracked, under independently controlled cracking condi- 3g tions', in aseparate heating coil of the system, or, as an alternative butnon-equivalent method of operation, a regulated portion or all of theenriched absorber oil may be returned to further treatment in the samecracking coil to which the charging stock is supplied. Although no attempt will be made here to explain the mechanism of the reactionsinvolved in this step of the process, I have found that, when theseselected intermediate liquid conversion products are sub- 4 jected tofurther cracking in the presence of the unsaturated relatively highboiling components of the gases, such as propylene and butenes, forexample, the yield of good quality gasoline may be materially increased.This may be due to polymerization of the unsaturated gases under thetemperature and pressure conditions employed in said separate heatingzone, or to some other reactionv between the unsaturated gases and.compounds contained in the oil with which they are commingled in saidseparate heating coil, or it may be due in part to both.

It will `be apparent from the foregoing that the invention combines thesteps of selective cracking and vreforming stabilization and absorptionin a cooperative and advantageous manner in a single unied systemwherein light distillates, such as gasoline, or gasoline fractions ofpoor antiknock value, naphtha and the like, may be treated to producehigh yields of good antiknock gasoline with minor yields of higherboiling liquid products and relatively light gases.

One specific embodiment oil the invention comprises subjectinghydrocarbon oil charging stock, such as low boiling distillatecontaining an appreciable quantity of materials Within the boiling rangeof gasoline, but of poor antiknock value, to

reforming conditions of cracking temperature and substantialsuperatmospheric pressure in a heating coil, removing from the resultingproducts, non-vaporous high-boiling components such as heavy polymersand residual liquids, separating the vaporous components of saidproducts, by fractionation, into selected relatively low-boiling andhigher boiling intermediate products and fractionated vapors of thedesired end boiling point and antiknock Value, removing said highboilingintermediate liquid products from the system, subjecting saidfractionated vapors to condensation, recovering and separating theresulting distillate and. uncondensed gases, subjecting said distillateto stabilization for the purpose of reducing its vapor pressure,recovering the stabilized distillate as the final gasoline product ofthe process, subjecting the gaseous products, including those evolvedfrom the distillate by stabilization, to absorption for the removaltherefrom of a desirable high-boiling components by intimatelycommingling said gases with said selected low-boiling fractions of `theintermediate liquid conversion products, subjecting the resultingenriched absorber oil to further treatment within the system undercracking conditions oi elevated temperature and substantialsuper-atmospheric pressure and subjecting resulting products to theaforementioned steps oi separation, fractionation, etc.

The accompanying diagrammatic drawing illustrates one specific form ofapparatus in which the process of the invention maybe accomplished.Referring to the drawing, hydrocarbon oil charging stock forthe'process, comprising a relatively low-boiling distillate containing asubstantial proportion of materials within the boiling range of motorfuel but oi poor antiknock value, such as straight-run or crackedgasoline, naphtha or the like, is supplied through line i and valve 2 topump A3 by means of which it is fed. through line 4 and valve 5 intoheating coil 6. The charging stock may, oi course, be preheated in anywell known manner, not illustrated in the drawing, prior to itsintroduction into the heating coil.

A furnace I of any suitable form supplies the required heat to the oilpassing through heating coil B to subject it to the desired conversionconditions of elevated temperature, preferably at a substantialsuperatmospheric pressure, and, although the heating coil is illustratedin a conventional manner in the drawing, it ls preferably' of such form,several modifications of which are now well known, that the oil may 'bebrought quickly to the desired conversion temperature and thenmaintained at or near the maximum temperature attained for apredetermined time.

The stream of hot conversion products is discharged from heating coil Ethrough line 8 and Valve 9 into column I D and, preferably, in order todefinitely control the conversion time as wel! as the temperature andpressure conditions to which the oil is subjected, provision is made forcooling Vthe stream of hot conversion products discharged from theheating coil sufficiently to prevent any substantial further conversionthereof. An appreciable reduction in the pressure imposed upon the oilas it passes through valve 9 serves to eiect appreciable cooling of theconversion products and assists their vaporization and fractionation incolumn I0. Provision is also made, in the case here illustrated, foreffecting any desired degree of additional cooling of the conversionproducts by directly commingling a suitable cooling liquid with thestream of products passing through line 8, by introducing the coolingmedium thereto through line II and valve' I2. The liquid utilized forthis purpose may comprise any desired oil, preferably of relativelylow-boiling characteristics, which will not contaminate the conversionproducts, and may include, for example, a regulated portion of thedistillate collected, as will be later more fully described, in receiver30 or regulated quantities of the intermediate liquid conversionproducts of the process recovered from column ID, as will be later morefully described.

Column II) comprises, in the particular case here illustrated, a lowerportion I 3, comprising a vaporizing and separating chamber, whereinnon-vaporous residual liquid conversion products, heavy polymerizationproducts and the like are separated from the vapors, and an upperportion or fractionating column I4 wherein two selected fractions of theintermediate products, comprising high-boiling components of the vapors,are condensed and separated from the overhead vaporous product, thelatter comprising materials of the desired end-boiling point andantiknock value within the range of gasoline and the normally gaseousTJroducts produced by the cracking operation.

Residual liquids, including high-boiling poly- 'merization products andthe like, may be removed from the lower portion I3 of column I0 throughline I and valve I6 to cooling and storage or elsewhere, as desired. l

The selected high boiling fractions of the intermediate liquidconversion products condensed in fractionator Il are, preferably,substantially devoid of materials within the boiling range of gasolineand comprise the intermediate liquid products which are not particularlysuitable for ,i

further cracking under high temperature and pressure conditions. Thismaterial may be allowed to accumulate in the lower portion offractionator I4, above a suitable partition I'I which separates theupper and lower portions of column I0, and it may be removed therefromthrough line 22 and valve 23 to cooling and storage or to any desiredfurther treatment. It is also within the scope of the invention toutilize regular quantitles of this material, preferably' after it hasbeen cooled to the desired degree, as a cooling medium in line 8 bysupplying the same thereto through line II and valve I2, by well knownmeans not illustrated, and/or. when a separate heating' coil suchasindicated at B8 is employed, this material may be utilized as a coolingmedium in discharge line 'I0 from this zone by suppling the same theretoin regulated quantities through line 'I2 and valve 13. It is also withinthe scope of the invention to blend high-boiling oils collected in thelower portion by fractionator I4' with the heavy residual liquidproducts removed from chamber I3, as previously described, through lineI5 and valve I8 and, although means for accomplishing this are notillustrated in the drawing, 'these materials may be blended eitherwithin or external to chamber'l3.

Selected low-boiling fractions of the intermediate liquid conversionproducts condensed in fractionator I4 may be withdrawn therefrom at vanysuitable intermediate point or plurality of points therein and, in thecase here illustrated,

'are directed throughV line 20 and valve 24 to pump 2 I, whereby theymay be supplied to further treatment within the system, as will be laterdescribed.

Fractionated vapors of the desired end-boiling point, comprising thefinal motor fuel product of 'ess gases, as will be later more fullydescribed.

Distillate is withdrawn from receiver 30 through line and valve 36 topump 31 by means of which it is supplied through line 38 and valve 39 tostabilization in stabilizer 40.

A regulated portion of the distillate collected in receiver 30may, whendesired, be recirculated by well known means, not shown in the drawing,

to the upper portion of fractionator I4 to serve asa cooling andrefluxing medium in this zone for assisting fractionation ofthe vaporsand to maintain the desired vapor outlet temperature from thefractionator.

The distillate supplied to stabilizer 40 is re-v boiled and subjectedkto partial vaporization in any suitable manner such as, for example, by

. means of a heating coil 4| located in the lower portion of thestabilizer, through which any suitable heating inedium such as steam,hot oil or the like may be passed. The reboiled and stabilizeddistillate is withdrawn from the lower portion of column 40 through line42 and valve 43 to cooling and storage or elsewhere, as desired. .Thelcomponents of the distillate vaporized in stabilizer 40 are subjectedtoV fractionation in this zone, whereby the undesirable low-boilingcomponents of the distillate and 'entrained gases are liberatedtherefrom so as toreduce the vapor pressure of the final motor fuelproduct.

The low-boiling materials liberated in stabilizer 40 are withdrawn fromthe upper portion of l this zone through line 44 and valve 45 and aredirected through valve 33 in line 3I to absorber 34. A regulated portionof the low-boiling materials from stabilizer 4I) may be diverted fromline II through line 46 and valve 41 to a condenser and., cooler 48, ofany suitable form capable of liquefying the high-boiling components ofthe normally gaseous materials, and the resulting distillate and gaspassesathrough line 49 and 50 to collection and separation in receiver5I. The distillate thus formed may be recirculated in regulatedquantities, by means 0f line 52, valve 53, pump 54, line 55 and valve56, to the upper portion of stabilizer 40` to serve as a reiluxing andcooling medium vin this zone, in order to assist fractionation of thevaporous products in the stabilizer and maintain the desired outlettemperature from this zone.

The uncondensed gases from receiver 5I may be directed, either alone ortogether with anyexcess quantity of distillate collected in thisreceiver and not required as reflux medium in stabilizer 40, throughline 51, valve 58 and line 3| to absorber 34. Provision is also made fordirecting regular quantitiesof the distillate collected in receiver 5I,comprising the quantity of vsuch material not required as a refluxmedium in stabilizer 40, from line 55, through line and valve 8| intoline, 66 wherefrom it may be returned through line 14 and valve 'i5 tofurther treatment in heating coil 6, together with the charging stock,or it may be directed, all or in part, through valve 61 in line 66 tofurther treatment in heating'coil 68, together with said selectedlow-boiling intermediate liquid products from fractionator I4.

The intermediate liquid conversion products supplied, as previouslydescribed, from fractionator I4 to pump 2l may be supplied, all or inpart, through line 59 and valve into the upper portion 'ofabsorber 34,wherein they serve as an absorber oil to remove from the gases suppliedto this zone desirable relatively highboiling components, includingpropylene, butenes and the corresponding saturated compounds. Therelatively lean gases remaining unabsorbed in column 34 are releasedfrom the upper portion of this zone through line 6I and valve 62 tostorage or elsewhere, as desired. The enriched absorber oil is withdrawnfrom the lower portion of column 34 through line 63 and valve 64 to pump65, by means of which it is fed through line 66 and may be directedthrough valve 61 in this line to further conversion in heating coil 68,or it may be directed through line 14, valve 15 and line 4 to conversionin heating coil 6, together with the charging stock.

When desired, a regulated portion or all of the selected relatively'lowboiling fractions supplied to pump 2I, as previously described, may bedirected from line 59 to further cracking in either heating coil 6 orheating coil 68, by means of the respective lines 18 and 1'6, controlledrespectively by valves 19 and 11.

Heating coil 68 is located in a suitable form of furnace 69 by means ofwhich, when this separate heating coil is employed, suiilcient heat issupplied to the oil passing through this zone to subject it to thedesired conversion temperature, preferably at a substantialsuperatmospheric pressure. Like heating coil 6 and furnace 1, heatingcoil 68 and furnace 69 are preferably of such form that the oil suppliedthereto may bel maintained therein at a temperature near the maximumattained for a predetermined time, although the heating coil isillust-rated in the drawing in a conventional manner.

The heated products from heating coil 89 are directed through line 10and valve 1I ,into the vaporizing and separating section I3 of column IIl, preferably being cooled suciently during their passage through line10 to prevent any excessive further conversion thereof. Valve 1I in line10 permits a substantial reduction in pressure between heating coil 68and chamber I3, whereby appreciable cooling of the hot conversionproducts from heating coil 68 is accomplished and whereby theirvaporization is as- Sisted in chamber I3 and, in addition, line 12 andvalve 13, communicating with line 10, are provided, whereby a suitablecooling medium may be commingled with the streamv of conversion productspassing from heating coil 68 to chamber I3, in order to further reducetheir temperature to the desired degree. Examples ofthe materials whichmay be employed as cooling liquid in line 10 have already been given inconnection with the cooling of the conversion products from heating coil6.

When the intermediate conversion products utilized as absorber oil inabsorber Il and thereafter subjected to further conversion include asubstantial proportion of intermediate conversion products boiling abovethe range of the charging stock, this \material is preferably subjectedto conversion in heating coil Alill, separate from the charging stock.The separate heating coil 08 may be employed for treatment of theintermediate conversion products in any case, when so desired. However,when the enriched absorber oil does not have an appreciably higherend-boiling point than the charging stock, it is normally subjected toconversion in heating coil i, together with the charging stock. f

The preferred range of operating conditions which may be employed toaccomplish the objects of the present invention, in an apparatus such asillustrated and above described, may be approximately as follows: Themaximum temperature to which the charging stock is subjected in theheating coil to which it is supplied may range, for example, from 950 to1050 F. and it is preferably maintained for a predetermined time at atemperature within approximately 50 or less ofthe maximum attained. It

is then cooled to'a temperature of the order of 700 to 800 F. oriless,"'and',introduced into the vaporizing 11nd separating chamber.tial superatmospheric pressure is preferably employod in `the heatingcoil ranging, for example, as measured at the outlet, from 300 tov 1000pounds, or more, per square inch. The vaporizing and separating chamberis preferably operated at a substantially reduced pressure relative tothat employed in the heating coil ranging, for example, from 150 pounds,or thereabouts, per square inch down to substantially atmosphericpressure. The pressure employed in the fractionating, condensing andcollecting portions of the system may be substantially the same or:lower than the pressure employed in the vaporiz-l ing and separatingchamber. The stabilizing column may be operated at any desired pressureranging from 250 pounds, or more, per square inch, gown to substantiallyatmospheric pressure, and any desired pressure within substantially thissame range may be employed in the absorption column.

When a separate heating coil is employed for conversion of the enrichedabsorber oil, the range of conditions which may be employed in this zoneare substantially the same as those which may be employed in the otherheating coil but the conditions employed in the two heating coils areindependently controlled and, normally, different conditions areutilized in the two heating coils.

As a specific example of the operation of the process of the invention,the charging stock, which .comprises gasoline of exceptionally pooranti-knock value, obtained from Michigan crude, is subjected to aconversion temperature, measured at the outlet of the heating coil towhich it is supplied, of approximately 980 F. at a superatmosphericpressure of about 800 pounds per square inch and, after being cooled toa temperature of approximately 750 F. by pressure reduction and bycommingling therewith regulated n quantities of the high boiling refluxcondensate,

A substanafter cooling the latter, is introduced into the vaporizing andfractionating column which is operated at a. superatmospheric pressureof approximately 60,.pounds per square inch. 'Ihis pressure issubstantially equalized in the condensing and collecting portions of thesystem, the stabilizing column is operated at a superatmosphericpressure of approximately 175 pounds per square inch and asuperatmospheric pressure of approximately 60 pounds per square inch ismaintained in the absorber. A gasoline product of approximately 400 F.end-boiling point is removed, in vaporous state, together with thegaseous products of the process, as the over-head stream from thefractionator, but fractionation is so controlled that the selectedintermediate liquid products removed as a side-stream from thefractionator include some materials boiling within the range as theover-head product as well as somewhat higher boiling materials. Thisproduct, which has a boiling range of approximately 270 to 550 F., issupplied to the absorber and, after being enriched by absorbing highboiling components of the process gases, it is subjected in a separateheating coil to an outlet conversion temperature of approximately 970 F.at a superatmospheric pressure of about 750 pounds per square inch. Thestream of conversion products from this zone is also cooled to atemperature of approximately 750 F. and then introduced into `thevaporizing chamber. High-boiling components of the intermediate liquidproducts condensed in the fractionator are recovered as a final-productof the process, as is also residual liquid Afrom the vaporizing chamber.The above described operation will produce, per barrel of chargingstock, approximately 78 per cent of 400 F. end-point gasoline having anoctane number of 70 or better by the motor method and approximately 800cubic feet of relatively lean gas, the remainder being chargeableprincipally to heavy liquid products.

I c-laim as my invention:

1. A process for the reforming of hydrocarbon distillates of low-boilingcharacteristics, which containI an appreciable quantity of fractions oflow antiknock value boiling within the range of gasoline, for the'purpose of producing a gasoline of materially improved antiknock value,which comprises subjecting the distillate in a heating zone to crackingconditions adequate to enhance its antiknock value, separating theresulting products into vaporous and non-vaporous components in aseparating zone, subjecting said vaporous components to fractionalcondensation to separate the same into a heavy reflux condensatesubstantially devoid of gasoline, a lighter reflux condensate containinghigh-boiling gasoline fractions, a distillate product containingsubstantially all of the low-boiling gasoline fractions in said vaporousproducts and a, normally gaseous product, recovering said distillateproduct, contacting at least a portion of said gaseous product with saidlighter reflux condensate to absorb high-boiling components includingpropylene and butenes of the former in the latter, subjecting resultantenriched lighter reflux condensate to 'cracking conditions oftemperature, pressure and time controlled independently of thoseemployed for the distillate charging 7stock and adequate to convert thesame into high yields of good antiknock gasoline, and subjecting thevaporous products of the last mentioned cracking step to said fractionalcondensation, to-

lalarms? gether with the vaporous products of the first mentionedcracking step. y

2. A process for the reforming of hydrocarbon distillates of low-boilingcharacteristics, which contain an appreciable quantity of fractions oflow antiknock value boiling within the range of gasoline, for thepurpose of producing a gasoline of materially improved antiknock value,which comprises subjecting the distillate in a heating zone to crackingconditions adequate to enhance its antiknock value, separating theresulting propylene and butenes in said lighter reiiux condensate,heating the resultant enriched lighter reflux condensate under crackingvconditions of' temperature, pressure and time controlled independentlyof those employed for the distillate charging stock and adequate toproduce high yields of good antiknock gasoline therefrom, and

ysubjecting the vaporous products of the last mentioned cracking step tosaid fractional condensation, together with said vap'orous products ofthe first mentioned crackingstep.

3. A process such as defined in claim 2 wheref in at least a portion ofthe first mentioned normally gaseous products are subjected toabsorption, together with said normally gaseous products from thestabilization step.

4. A conversion process which Lcomprises subjecting a light paraflinicoil of the character of gasoline and naphtha to reforming conditions oftemperature and pressure in a conversion zone and fractionating theresultant vapors and gases to condense and separate fractions thereofheavier than gasoline, further fractionating-the uncondensed gasolinevapors and gases to separate therefrom an intermediate condensatecontaining heavy gasoline fractions of inferior antiknock value,`subjecting the remaining light gasoline vapors and gases to finalcondensation under sufficient pressure to liquefy a substantial portionof the gases with the light gasoline vapors,`

stabilizing the resultant final condensate to remove normally gaseoushydrocarbons therefrom,

combining at least a portion of said gaseous hy-` drocarbons, includingpolymerizable voleiins, with a substantial portion, at least, of saidintermediate condensate, subjecting the resultant mixture in a secondconversion zone to independently controlled conditions of temperatureand pressure adequate to reformv the intermediate condensate andpolymerize normally gasf eous olefins, and recovering from ltheresultant products a distillate boiling within the gasoline range.

5. A conversion process which comprises subjecting a light parafiinicoil of the character of gasoline and naphtha to reforming conditions oftemperature and pressure in a conversion zone and fractionating theresultant vapors and gases to condense and separate fractions thereofheavier than gasoline, further fractionating the uncondensed gasolinevapors and gases to separate therefrom an intermediate condensatecontaining heavy gasoline fractions of interior antivknock value,subjecting the remaining light gasoline vapors and gases to finalcondensation under sufficient pressure to liquefy a substantial portionof the gases with the light gasoline vapors, stabilizing the resultantfinal condensate to remove normally gaseous hydrocarbons therefrom,scrubbing the latter with at least a p0rtion of said intermediatecondensate to absorb polymerizable gaseous olens in the condensate,

subjecting the thus enriched intermediate condensate in a secondconversion zone to independently controlled conditions of temperatureand pressure adequate to reform the intermediate condensate andpolymerize normally gaseous oleflns, and recovering from the resultantproducts a distillate boiling within the gasoline range.

KENNETH SWARTWOOD.

